This is a project I have wanted to do for a while. The baud rate overlapping with the frequency was something I had never considered and will be a problem for my own project to store MFM data on cassette. The infographic pdf was a great way to demonstrate the frequency.
It's fascinating how cassette interfaces were implemented in different countries. The rationale behind the "we store pulses" is explained in "The TV Typewriter Cookbook" as tape drives having lots of wow and flutter and not being at the correct speed. The German devices with tape interface I've seen so far all had simple half-duplex V.23 modems.
Very nice. I'd been mulling over the idea recently of using a US(A)RT to generate an MFM signal, similar to 9-track tape, for a cassette interface. This could push the bitrate up to somewhere near 2400 baud, potentially, and would be easily decoded using a PLL or phase detector. I suppose that wouldn't put the on-tape format that far off from something like a floppy disk. The only issue I've been really looking at is filtering - audio cassettes tend to record lots of harmonics with fast level transitions, and without narrow filtering that could be a problem for reading data back.
Not so sure about that. In the early 90s, I made a Sinclair ZX Spectrum simulator for my PCs. There, I managed to read ZX Spectrum's 1500 baud (bits/second) casette tapes using just a TTL port on the PC (one bit of the printer port). No filters of any kind used. (The first version was in assembly for a 12 MHz 286, and a later version in Pascal for my new and fancy 25 MHz 486 :)
20:56 I spotted that Iomega-branded SCSI cable... I suppose that DB-25 SCSI 1 cables are no different than a straight-thru RS232 cable internally, but I got a kick out of seeing a 3-decade-newer Zip drive cable carry serial data from a 1976-era machine :P
This is a project I have wanted to do for a while. The baud rate overlapping with the frequency was something I had never considered and will be a problem for my own project to store MFM data on cassette. The infographic pdf was a great way to demonstrate the frequency.
I never knew there were so many aspects to the cassette interface.
It's fascinating how cassette interfaces were implemented in different countries. The rationale behind the "we store pulses" is explained in "The TV Typewriter Cookbook" as tape drives having lots of wow and flutter and not being at the correct speed. The German devices with tape interface I've seen so far all had simple half-duplex V.23 modems.
Very nice. I'd been mulling over the idea recently of using a US(A)RT to generate an MFM signal, similar to 9-track tape, for a cassette interface. This could push the bitrate up to somewhere near 2400 baud, potentially, and would be easily decoded using a PLL or phase detector. I suppose that wouldn't put the on-tape format that far off from something like a floppy disk. The only issue I've been really looking at is filtering - audio cassettes tend to record lots of harmonics with fast level transitions, and without narrow filtering that could be a problem for reading data back.
Not so sure about that. In the early 90s, I made a Sinclair ZX Spectrum simulator for my PCs.
There, I managed to read ZX Spectrum's 1500 baud (bits/second) casette tapes using just a TTL port on the PC (one bit of the printer port).
No filters of any kind used.
(The first version was in assembly for a 12 MHz 286, and a later version in Pascal for my new and fancy 25 MHz 486 :)
Nice
20:56 I spotted that Iomega-branded SCSI cable... I suppose that DB-25 SCSI 1 cables are no different than a straight-thru RS232 cable internally, but I got a kick out of seeing a 3-decade-newer Zip drive cable carry serial data from a 1976-era machine :P
Am i commenters, or at you?
Changing the cassette interface is fun, QFM is next right?
If you can code that many data bits why dont you.